1. Field of the Invention
The present invention relates to umbrellas and more particularly, to an operating mechanism for umbrella, which uses screw rods and screw nuts to move the telescopic umbrella shaft between the extended position and the received position, thereby moving the runner to open or close the umbrella canopy.
2. Description of the Related Art
Many automatic umbrellas are commercially available. These conventional automatic umbrellas have drawbacks as follows:    1. When released the lock, the runner is suddenly forced by the spring force of the related spring member to push the umbrella stretchers against the umbrella ribs, opening the umbrella canopy in a rush. Sudden open of the umbrella canopy may injure other persons accidentally.    2. After the umbrella canopy is opened, the runner is not locked, and the umbrella canopy may be forced by a strong wind to collapse the umbrella stretchers and the umbrella ribs.    3. The spring member will start to deteriorate after a long use of the umbrella, affecting normal functioning of the umbrella.